import random import sys def test_strat(strat, hashpower, gamma, reward, fees, uncle_rewards=1, uncle_coeff=0, max_uncles=2, rounds=25000): # Block reward for attacker me_reward = 0 # Block reward for others them_reward = 0 # Fees for the attacker me_fees = 0 # Fees for others them_fees = 0 # Blocks in current private chain me_blocks = 0 # Blocks in current public chain them_blocks = 0 # Time elapsed since last chain merging time_elapsed = 0 # Divisor for block rewards (diff adjustment) divisor = 0 # Total blocks included from attacker me_totblocks = 0 # Total blocks included from others them_totblocks = 0 # Uncles included from attacker me_totuncles = 0 # Uncles included from others them_totuncles = 0 # Simulate the system for i in range(rounds): # Attacker makes a block if random.random() < hashpower: me_blocks += 1 last_is_me = 1 # Honest nodes make a block else: them_blocks += 1 last_is_me = 0 time_elapsed += random.expovariate(1) # "Adopt" or "override" if me_blocks >= len(strat) or them_blocks >= len(strat[me_blocks]) or strat[me_blocks][them_blocks] == 1: # Override if me_blocks > them_blocks or (me_blocks == them_blocks and random.random() < gamma): me_reward += me_blocks * reward - (reward if me_blocks and them_blocks else 0) me_fees += time_elapsed * fees divisor += me_blocks - (1 if me_blocks and them_blocks else 0) me_totblocks += me_blocks # Add uncles while me_blocks < 7 and them_blocks > 0: r = min(them_blocks, max_uncles) * (0.875 - 0.125 * me_blocks) * uncle_rewards them_totuncles += min(them_blocks, max_uncles) divisor += min(them_blocks, max_uncles) * uncle_coeff them_reward = them_reward + r them_blocks -= min(them_blocks, max_uncles) me_blocks += 1 # Adopt else: them_reward += them_blocks * reward - (reward if me_blocks and them_blocks else 0) them_fees += time_elapsed * fees divisor += them_blocks - (1 if me_blocks and them_blocks else 0) them_totblocks += them_blocks # Add uncles while them_blocks < 7 and me_blocks > 0: r = min(me_blocks, max_uncles) * (0.875 - 0.125 * them_blocks) * uncle_rewards me_totuncles += min(me_blocks, max_uncles) divisor += min(me_blocks, max_uncles) * uncle_coeff me_reward = me_reward + r me_blocks -= min(me_blocks, max_uncles) them_blocks += 1 me_blocks = 0 them_blocks = 0 time_elapsed = 0 # Match elif strat[me_blocks][them_blocks] == 2 and not last_is_me: if random.random() < gamma: me_reward += me_blocks * reward + time_elapsed * fees - (reward if me_blocks and them_blocks else 0) me_totblocks += me_blocks divisor += me_blocks - (1 if me_blocks and them_blocks else 0) time_elapsed = 0 # Add uncles while me_blocks < 7 and them_blocks > 0: r = min(them_blocks, max_uncles) * (0.875 - 0.125 * me_blocks) * uncle_rewards them_totuncles += min(them_blocks, max_uncles) divisor += min(them_blocks, max_uncles) * uncle_coeff them_reward = them_reward + r them_blocks -= min(them_blocks, max_uncles) me_blocks += 1 me_blocks = 0 them_blocks = 0 # print 'rat', (me_totblocks + me_totuncles) / (me_totblocks + me_totuncles + them_totblocks + them_totuncles * 1.0) return me_reward / divisor + me_fees / rounds, them_reward / divisor + them_fees / rounds # A 20x20 array meaning "what to do if I made i blocks and the network # made j blocks?". 1 = publish, 0 = do nothing. def gen_selfish_mining_strat(): o = [([0] * 20) for i in range(20)] for me in range(20): for them in range(20): # Adopt if them == 1 and me == 0: o[me][them] = 1 if them == me + 1: o[me][them] = 1 # Overtake if me >= 2 and me == them + 1: o[me][them] = 1 # Match if me >= 1 and me == them: o[me][them] = 2 return o dic = {"rewards": 1, "fees": 0, "gamma": 0.5, "uncle_coeff": 0, "uncle_rewards": 0, "max_uncles": 2} for a in sys.argv[1:]: param, val = a[:a.index('=')], a[a.index('=')+1:] dic[param] = float(val) print dic s = gen_selfish_mining_strat() for i in range(1, 50): x, y = test_strat(s, i * 0.01, dic["gamma"], dic["rewards"], dic["fees"], dic["uncle_rewards"], dic["uncle_coeff"], dic["max_uncles"], rounds=200000) print '%d%% hashpower, %f%% of rewards, (%f attacker, %f honest)' % \ (i, x * 100.0 / (x + y), x * 100.0 / i, y * 100.0 / (100-i))